Refrigerant system

ABSTRACT

A refrigerant system is provided. The refrigerant system may use an electronic expansion valve that electronically controls an opening degree thereof, as a high-pressure valve and a low-pressure valve to selectively block a high-pressure branch valve and a low-pressure branch valve. Accordingly, noise transmitted to an interior space may be minimized when the operation mode of the refrigerant system is switched. In addition, the structure of the refrigerant system may be simplified.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119 and 35U.S.C. 365 to Korean Patent Application No. 10-2010-0011587 (filed onFeb. 8, 2010), which is hereby incorporated by reference in itsentirety.

BACKGROUND

The present disclosure relates to a refrigerant system in which arefrigerant cycle is performed.

In general, a refrigerant system is a device that cools or heats aninterior space by performing a refrigerant cycle including compression,condensation, expansion and evaporation of refrigerant.

The refrigerant system includes an indoor unit in which a refrigerant isheat-exchanged with indoor air and an outdoor unit in which arefrigerant is heat-exchanged with outdoor air. The indoor unit includesan indoor heat exchanger for performing heat-exchange between therefrigerant and the indoor air, a fan blowing the indoor air, and amotor rotating the fan. The outdoor includes an outdoor heat exchangerfor performing heat-exchange between the refrigerant and the outdoorair, a fan for blowing the outdoor air, a motor for rotating the fan, acompressor for compressing the refrigerant, an expander for expandingthe compressed refrigerant, and a 4-way valve for diverting a flow ofthe refrigerant.

When an interior space is cooled, the indoor heat exchanger operates asan evaporator, and the outdoor heat exchanger operates as a condenser.When the interior space is heated, the indoor heat exchanger operates asa condenser, and the outdoor heat exchanger operates as an evaporator.The 4-way valve diverts a refrigerant flow direction to switch thecooling and heating operations.

SUMMARY

Embodiments provide a refrigerant system capable of minimizing interiornoise when an operation mode is switched, while simplifying thestructure thereof.

In one embodiment, a refrigerant system includes: an outdoor unitcomprising an outdoor heat exchanger in which a refrigerant and outdoorair are heat-exchanged with each other and a compressor compressing therefrigerant, a plurality of indoor units, each comprising an indoor heatexchanger in which the refrigerant and indoor air are heat-exchangedwith each other, a high-pressure tube guiding the refrigerant dischargedfrom the compressor to the plurality of indoor heat exchangers, alow-pressure tube guiding the refrigerant evaporated in at least one ofthe indoor heat exchangers to the compressor, a high-pressure branchtube branched from the high-pressure tube to guide the refrigerant inthe high-pressure tube to any one of the indoor heat exchangers, alow-pressure branch tube branched from the low-pressure tube to guidethe refrigerant into the any one of the indoor heat exchangers to thelow-pressure tube, an indoor unit tube connecting the any one of theindoor heat exchangers to both the high-pressure branch tube and thelow-pressure branch tube, and a high-pressure valve and a low-pressurevalve mounted on the high-pressure branch tube and the low-pressurebranch tube to selectively block the refrigerant flows in thehigh-pressure branch tube and the low-pressure branch tube,respectively, wherein each of the high-pressure valve and thelow-pressure valve comprises an electronic expansion valve toelectronically control an opening degree thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a state in which cooling and heating operations aresimultaneously performed in a refrigerant system according to anembodiment.

FIG. 2 is a view showing a flow of refrigerant while an indoor unit ofthe refrigerant system is operating in a heating mode.

FIG. 3 is a view showing the refrigerant flow while the indoor unit ofthe refrigerant system is switching from the heating mode to a coolingmode.

FIG. 4 is a view showing the refrigerant flow while the indoor unit ofthe refrigerant system is operating in the cooling mode.

FIG. 5 is a view showing the refrigerant flow while the indoor unit ofthe refrigerant system is switching from the cooling mode to the heatingmode.

FIG. 6 is a view showing the refrigerant system operating in a fullcooling mode.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the embodiments of the presentdisclosure, examples of which are illustrated in the accompanyingdrawings.

In the following detailed description of the preferred embodiments,reference is made to the accompanying drawings that form a part hereof,and in which is shown by way of illustration specific preferredembodiments in which the invention may be practiced. These embodimentsare described in sufficient detail to enable those skilled in the art topractice the invention, and it is understood that other embodiments maybe utilized and that logical structural, mechanical, electrical, andchemical changes may be made without departing from the spirit or scopeof the invention. To avoid detail not necessary to enable those skilledin the art to practice the invention, the description may omit certaininformation known to those skilled in the art. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined only by the appended claims.

FIG. 1 is a view of a state in which cooling and heating operations aresimultaneously performed in a refrigerant system according to anembodiment.

Referring to FIG. 1, a refrigerant system includes an outdoor unit 1disposed in an outdoor space and exposed to outdoor air, a plurality ofindoor units 2 disposed in an indoor space and exposed to indoor air, adistributor 3 connecting the outdoor unit 1 to the plurality of indoorunits 2, and a refrigerant tube through which a refrigerant flows amongthe outdoor unit 1, the indoor units 2, and the distributor 3.

In detail, the outdoor unit 1 includes an outdoor heat exchanger 11 inwhich the indoor air and the refrigerant are heat-exchanged with eachother, a compressor 12 compressing the refrigerant, a flow switch part13 switching a flow direction of the refrigerant discharged from thecompressor 12, and an outdoor expansion part 14 selectively expandingthe refrigerant flowing into the outdoor heat exchanger 11.

The outdoor heat exchanger 11 is exposed to the outdoor air within theoutdoor unit 11. The outdoor heat exchanger 11 may selectively serve asan evaporator evaporating the refrigerant or a condenser condensing therefrigerant according to operation modes of the refrigerant system.

The compressor 12 includes a constant speed compressor 121 operated at aconstant speed to compress the refrigerant and an inverter compressor122 operated at a variable speed to compress the refrigerant. Theconstant speed compressor 121 and the inverter compressor 122 areparallely connected to each other.

The flow switch part 13 is disposed in the refrigerant tubecorresponding to a discharge side of the compressor 12. The flow switchpart 13 allows the refrigerant tube connected to an inflow side of thecompressor 12 to selectively communicate with the refrigerant tubeconnected to the outdoor heat exchanger 11 and the refrigerant tubecorresponding to the discharge side of the compressor 12. That is, therefrigerant discharged from the compressor 12 may flow into the outdoorheat exchanger 11 and vice versa according to the switching operation ofthe flow switch part 13.

The outdoor expansion part 14 is disposed in the refrigerant tubecorresponding to a position adjacent to the outdoor heat exchanger 11.Particularly, the outdoor expansion part 14 is disposed in therefrigerant tube connecting the outdoor heat exchanger 11 to thedistributor 3. When the refrigerant system is operated to allow theoutdoor heat exchanger 11 to serve as the evaporator, the refrigerantdischarged from the distributor 3 may be expanded while it passesthrough the outdoor expansion part 14 before it flows into the outdoorheat exchanger 11.

Furthermore, the outdoor unit 1 may further include an outdoor fan (notshown) for forcibly blowing the outdoor air toward the outdoor heatexchanger 11 and an outdoor motor (not shown) for rotating the outdoorfan.

Each of the indoor units 2 includes an indoor heat exchanger 23 in whichthe indoor air and the refrigerant are heat-exchanged with each otherand an indoor expansion part 24 for expanding the refrigerant flowinginto the indoor heat exchanger 23. That is, the refrigerant systemincludes a plurality of the indoor heat exchangers 23 and a plurality ofthe indoor expansion parts 24 corresponding to the plurality of indoorheat exchangers 23 as a whole.

The distributor 3 is connected to both the outdoor unit 1 and theplurality of indoor units 2. The distributor distributes the refrigerantdischarged from the outdoor unit 1 to the plurality of indoor units.Also, the distributor 3 switches a flow direction of the refrigerantwithin the indoor units 2 according to the operation mode of therefrigerant system.

The refrigerant tube includes a high-pressure tube 42 guiding therefrigerant discharged from the compressor 12 to the distributor 3, alow-pressure tube 43 guiding the refrigerant evaporated by at least oneof the indoor units 2 to the compressor 12, and a liquid refrigeranttube 41 through which the refrigerant condensed within the indoor units2 or the outdoor until flows, and an indoor unit tube 44 connecting thedistributor 3 to the indoor units 2.

The high-pressure tube 42, the low-pressure tube 43, and the liquidrefrigerant tube 41 connect the outdoor unit 1 to the distributor 3.Also, the high-pressure tube 42 is branched from the refrigerant tubecorresponding to the discharge side of the compressor 12 to extend up tothe inside of the distributor 3. The low-pressure tube 43 is connectedto the refrigerant tube corresponding to the inflow side of thecompressor 12 to extend up to the inside of the distributor 3. Also, theliquid refrigerant tube 41 is connected to the outdoor expansion part 14to extend up to the inside of the distributor 3.

The distributor 3 includes a plurality of high-pressure branch tubes 45guiding the refrigerant within the high-pressure tube 42 to theplurality of indoor heat exchangers 23, a plurality of low-pressurebranch tubes 46 guiding the refrigerant within the plurality of outdoorheat exchangers 11 to the low-pressure tube 43, and high-pressure andlow-pressure valves 31 and 32 respectively selectively interrupting therefrigerant flows within the high-pressure and low-pressure branch tubes45 and 46.

That is, the high-pressure branch tube 45 is branched from thehigh-pressure tube 42, and the low-pressure branch tube 46 is branchedfrom the low-pressure tube 43. The high-pressure valve 31 and thelow-pressure valve 32 are disposed in the high-pressure branch tube 45and the low-pressure branch tube 46, respectively. The high-pressurevalves 31 and the low-pressure valves 32 may include an electronicexpansion valve capable of electronically controlling an opening degreethereof. The high-pressure valves 31 and the low-pressure valves 32include electronic expansion valves 311, 312, 321 and 322 havingdifferent capacities from one another. More specifically, thehigh-pressure valves 31 include the first electronic expansion valve311, and the second electronic expansion valve 312 having a smallercapacity than the first electronic expansion valve 311. The low-pressurevalves 32 include the third electronic expansion valve 321, and thefourth electronic expansion valve 322 having a smaller capacity than thethird electronic expansion valve 321. The first and the secondelectronic expansion valves 311 and 312 are mounted parallel on thehigh-pressure branch tube 45. The third and the fourth electronicexpansion valves 321 and 322 are mounted in parallel on the low-pressurebranch tube 46.

The indoor unit 44 has one end connected to the liquid refrigerant tube41 and the other end connected to both the high-pressure branch tube 45and the low-pressure branch tube 46. The indoor heat exchanger 23 andthe indoor expansion part 24 are mounted on the indoor unit tube 44.That is, the indoor unit tube 44 connects the indoor heat exchanger 23,the high-pressure branch tube 45, and the low-pressure branch tube 46 toone another.

Also, according to the operation mode of the indoor unit 2, therefrigerant in the liquid refrigerant tube 41 may sequentially passthrough the indoor expansion part 24 and the indoor heat exchanger 23 toflow into the low-pressure branch tube 46, or the refrigerant in thehigh-pressure branch tube 45 may sequentially pass through the indoorheat exchanger 23 and the indoor expansion part 24 to flow into theliquid refrigerant tube 41.

The outdoor expansion part 14 and the indoor expansion part 24 may alsoinclude an electronic expansion valve that controls an opening degreethereof according to the operation mode of the refrigerant system.

Hereinafter, a flow of the refrigerant in the refrigerant systemaccording to an embodiment will be described in detail with reference tothe accompanying drawings.

Referring to FIG. 1, in the refrigerant system, the plurality of indoorunits 2 may be operated in different operation modes simultaneously.FIG. 1 shows a refrigerant flow in a case where the outdoor heatexchanger 11 serves as a condenser, a first indoor unit 21 of the indoorunits 2 is operated in a heating mode, and a second indoor unit 22 isoperated in a cooling mode.

The refrigerant discharged from the compressor 12 is introduced into theoutdoor heat exchanger 11 by the flow switch part 13. Here, a part ofthe refrigerant discharged from the compressor 12 flows into thehigh-pressure tube 42.

First, the refrigerant introduced into the outdoor heat exchanger 11emits heat to the outdoor air while passing through the outdoor heatexchanger 11, thereby being condensed. The refrigerant passed throughthe outdoor heat exchanger 11 flows into the liquid refrigerant tube 41.At this process, even through the refrigerant passes through the outdoorexpansion part 14, the refrigerant passes through the outdoor expansionpart 14 without changing a phase thereof because the outdoor expansionpart 14 is fully opened.

The refrigerant flowed into the liquid refrigerant tube 41 flows towardthe first indoor unit 21 along the indoor unit tube 44 of the firstindoor unit 21. The refrigerant flowed into the first indoor unit 21 isexpanded while passing through the indoor expansion part 24 of the firstindoor unit 21. The refrigerant passed through the indoor expansion part24 absorbs heat from the indoor air while passing through the indoorheat exchanger 23 of the first indoor unit 21, thereby being evaporated.That is, the first indoor unit 21 is operated in the cooling mode.

Furthermore, the refrigerant passed through the indoor heat exchanger 23of the first indoor unit 21 is introduced into the low-pressure tube 43along the low-pressure branch tube 46 corresponding to the first indoorunit 21. Here, the high-pressure valves 31 corresponding to the firstindoor unit 21 are maintained in a closed state whereas the low-pressurevalves 32 corresponding to the first indoor unit 21 are maintained in anopened state. Therefore, the refrigerant discharged from the indoor heatexchanger 23, that is, the first indoor unit 21 may all smoothly flowinto the low-pressure tube 43.

The refrigerant flowing into the low-pressure tube 43 passes through thecompressor 12 and therefore compressed again.

The refrigerant discharged from the compressor 12 and flowed into thehigh-pressure tube 42 passes through the high-pressure branch tube 45corresponding to the second indoor unit 22, and then flows into theindoor unit tube 44 of the second indoor unit 22. At this process, thelow-pressure valves 32 corresponding to the second indoor unit 22 aremaintained in a fully closed state, and the high-pressure valves 31corresponding to the second indoor unit 22 are maintained in a fullyopened state. Therefore, the refrigerant passed through thehigh-pressure tube 42 and the high-pressure branch tube 45 may allsmoothly flow to the indoor heat exchanger 23, that is, the secondindoor unit 22.

The refrigerant emits heat to the indoor air while it passes through theindoor heat exchanger 23 of the second indoor unit 22, thereby beingcondensed. In other words, the second indoor unit 22 is operated in theheating mode. The refrigerant passed through the indoor heat exchanger23 flows into the liquid refrigerant tube 41 through the indoor unittube 44. Here, even though the refrigerant passed through the indoorheat exchanger 23 passes through the indoor expansion part 24, therefrigerant passes through the indoor expansion part 24 without changinga phase thereof because the indoor expansion part 24 is fully opened.

The refrigerant flowed into the liquid refrigerant tube 41 is mixed withthe refrigerant flowing from the outdoor unit 1 to the distributor 3. Asdescribed above, the mixed refrigerant passes through the first indoorunit 21, flows into the compressor 12 through the low-pressure tube 43,and is compressed again.

The outdoor heat exchanger 11 may function as a condenser or anevaporator according to the operation mode of the indoor units 2. Forexample, the outdoor heat exchanger 11 functions as the condenser whenall the indoor units 2 are operated in the cooling mode, or as theevaporator when all the indoor units 2 are operated in the heating mode.

When the outdoor heat exchanger 11 functions as the condenser, the flowswitch part 13 is configured to provide fluid communication between therefrigerant tube connected to the outdoor heat exchanger 11 and therefrigerant tube connected to the discharge side of the compressor 12.When the outdoor heat exchanger 11 functions as the evaporator, the flowswitch part 13 is configured to provide fluid communication between therefrigerant tube connected to the outdoor heat exchanger 11 and therefrigerant tube connected to the intake side of the compressor 12.

With respect to the liquid refrigerant tube 41, the refrigerant in theliquid refrigerant tube 41 flows toward the distributor 3 and the indoorunits 2 when the outdoor heat exchanger 11 functions as the condenser.On the other hand, when the outdoor heat exchanger 11 functions as theevaporator, the refrigerant in the liquid refrigerant tube 41 flowstoward the outdoor unit 1.

The operation mode of the indoor units 2 may be switched into any one ofthe cooling mode and the heating mode according to opening and closingoperations of the high-pressure valves 31 and the low-pressure valves32. For example, when the high-pressure valves 31 are closed and thelow-pressure valves 32 are opened in the first indoor unit 21, the firstindoor unit 21 is operated in the cooling mode. However, when thelow-pressure valves 32 are closed and the high-pressure valves 31 areopened in the second indoor unit 22, the second indoor unit 22 isoperated in the heating mode. That is, any one of the indoor units 2 maybe operated in the cooling mode or the heating mode according to openingand closing operations of the high-pressure valves 31 and thelow-pressure valves 32 of the corresponding indoor unit 2.

Hereinafter, a process of switching the operation mode in therefrigerant system will be described in detail with reference to theaccompanying drawings.

FIG. 2 shows a flow of the refrigerant while the indoor unit of therefrigerant system is operating in the heating mode. FIG. 3 shows therefrigerant flow while the indoor unit of the refrigerant system isswitching from the heating mode to the cooling mode. FIG. 4 shows therefrigerant flow while the indoor unit of the refrigerant system isoperating in the cooling mode, and FIG. 5 shows the refrigerant flowwhile the indoor unit of the refrigerant system is switching from thecooling mode to the heating mode.

Referring to FIG. 2, the high-pressure valves 31 are opened whereas thelow-pressure valves 32 are closed during the heating mode of the indoorunit 2.

Accordingly, the refrigerant in the high-pressure tube 42 flows into theindoor unit tube 44 through the high-pressure branch tube 45. Therefrigerant flowed into the indoor unit tube 44 emits heat to the indoorair while passing through the indoor heat exchanger 23, thereby beingcondensed. Next, the refrigerant passed through the indoor heatexchanger 23 flows into the liquid refrigerant tube 41 through theindoor unit tube 44.

However, in some cases, the indoor unit 2 may be switched from theheating mode to the cooling mode during the operation of the refrigerantsystem.

Referring to FIGS. 3 and 4, when the heating mode of the indoor unit 2is switched to the cooling mode, the indoor expansion part 24, thehigh-pressure valves 31, and the low-pressure valves 32 are all closedfirst. Therefore, a high-pressure refrigerant is shut in the refrigeranttube disposed among the indoor expansion part 24, the high-pressurevalves 31 and the low-pressure valves 32.

Next, the third electronic expansion valve 321 of the low-pressurevalves 32 is maintained in the closed state, and the fourth electronicexpansion valve 322 is opened. As a result, the high-pressurerefrigerant shut in the refrigerant tube among the indoor expansion part24, the high-pressure valves 31, and the low-pressure valves 32 flowsinto the low-pressure tube 43 through the low-pressure branch tube 46having a relatively low pressure.

As the fourth electronic expansion valve 322 is opened, the refrigeranttube among the indoor expansion part 24, the high-pressure valves 31,and the low-pressure valves 32 is balanced in pressure with thelow-pressure tube 43. Accordingly, the indoor expansion part 24 and thethird electronic expansion valve 321 are also opened. The refrigerant inthe liquid refrigerant tube 41 flows into the low-pressure branch tube46 having a relatively low pressure through the indoor unit tube 44.That is, the refrigerant flows into the low-pressure branch tube 46after it sequentially passes through the indoor expansion part 24 andthe indoor heat exchanger 23.

Here, the indoor expansion part 24 is partially opened to allow therefrigerant to expand and flow. More specifically, the refrigerant isexpanded while passing through the indoor expansion part 24 and thenflows into the indoor heat exchanger 23. In addition, the refrigerantabsorbs heat from the indoor air while passing through the indoor heatexchanger 23. That is, the indoor unit 2 operates in the cooling mode.The flow of refrigerant in the cooling mode of the indoor unit 2 isillustrated in FIG. 4.

The indoor unit 2 may be switched from the heating mode to the coolingmode through the above-described processes.

Also, in some cases, the indoor unit 2 may be switched from the coolingmode to the heating mode during the operation of the refrigerant system.

Referring to FIGS. 2 and 5, when the cooling mode of the indoor unit 2is switched to the heating mode, the indoor expansion part 24, thehigh-pressure valves 31 and the low-pressure valves 32 are all closedfirst. Therefore, a low-pressure refrigerant is shut in the refrigeranttube disposed among the indoor expansion part 24, the high-pressurevalves 31 and the low-pressure valves 32.

The first electronic expansion valve 311 of the high-pressure valves 31is maintained in the closed state whereas the second electronicexpansion valve 312 is opened. As a result, the low-pressure refrigerantin the high-pressure tube 42 flows into the refrigerant tube having arelatively low pressure and disposed among the indoor expansion part 24,the high-pressure valves 31 and the low-pressure valves 32 through thehigh-pressure branch tube 45.

As the second electronic expansion valve 312 is opened, the refrigeranttube disposed among the indoor expansion part 24, the high-pressurevalves 31 and the low-pressure valves 32 is balanced in pressure withthe high-pressure tube 42. Accordingly, the indoor expansion part 24 andthe third electronic expansion valve 321 are also opened. Therefore, therefrigerant in the high-pressure tube 42 flows into the liquidrefrigerant tube 41 having a relatively low pressure through the indoorunit tube 44. That is, the refrigerant flows into the liquid refrigeranttube 41 after it sequentially passes through the indoor heat exchanger23 and the indoor expansion part 24.

Here, since the indoor expansion part 24 is fully opened, therefrigerant may pass through the indoor expansion part 24 without aphase change. Also, the refrigerant emits heat to the indoor air whilepassing through the indoor heat exchanger 23. That is, the indoor unit 2operates in the heating mode. The flow of refrigerant in the heatingmode of the indoor unit 2 is illustrated in FIG. 2.

The indoor unit 2 may switch from the cooling mode to the heating modethrough the above processes.

According to the above-structured refrigerant system, noise generatedfrom the indoor heat exchanger 23, that is, the indoor unit 2 may beminimized during switching between the cooling mode and the heatingmode.

In further detail, when the indoor unit 2 switches from any one of thecooling mode and the heating mode to the other, the high-pressurerefrigerant and the low-pressure refrigerant are mixed according theopening and closing of the high-pressure valves 31 and the low-pressurevalves 32.

When the operation mode of the indoor unit 2 is switched by therefrigerant system, the second electronic expansion valve 312 having arelatively small capacity of the high-pressure valves 31 or the fourthelectronic expansion valve 322 having a smaller capacity of thelow-pressure valves 32 is opened first. Therefore, the high-pressurerefrigerant and the low-pressure refrigerant are mixed more slowly witheach other. As a consequence, impact and noise caused when thehigh-pressure refrigerant and the low-pressure refrigerant are mixed maybe minimized.

Furthermore, impact and noise transmitted to the interior space throughthe indoor unit tube 44 may also be minimized.

Hereinafter, a process of preventing exhaustion of the refrigerant whilethe refrigerant system is operating in a full cooling mode will bedescribed in detail with reference to the accompanying drawings.

FIG. 6 is a view showing the refrigerant system operating in a fullcooling mode.

Referring to FIG. 6, when the refrigerant system is in the full coolingmode, the refrigerant condensed in the outdoor heat exchanger 11 flowsinto all the indoor units 2 through the liquid refrigerant tube 41. Therefrigerant in the liquid refrigerant tube 41 all flows into the indoorunit tube 44 and absorbs heat from the indoor air while it passesthrough the indoor heat exchangers 23.

In this process, since the low-pressure valves 32 and the secondelectronic expansion valves 312 of the high-pressure valves 31 aremaintained in the opened state, the refrigerant passed through theindoor heat exchangers 23 flows to the low-pressure tube 43 through thelow-pressure branch tubes 46.

Here, regarding each of the indoor units 2, the refrigerant in thehigh-pressure branch tube 45 has a high temperature and a high pressure.On the other hand, the refrigerant in the indoor unit tube 44 and thelow-pressure branch tube 46, which correspond to a downstream of theindoor heat exchanger 23, has a low temperature and a low pressure.Therefore, the refrigerant in the high-pressure branch tube 45 adjacentto the indoor unit tube 44 and the low-pressure branch tube 46 is cooledby the refrigerant in the indoor unit tube 44 and the low-pressurebranch tube 46. Accordingly, a liquid refrigerant condensed by therefrigerant in the indoor unit tube 44 and the low-pressure branch tube46 may be generated in the high-pressure branch tube 45. Since therefrigerant in the high-pressure branch tube 45 is relatively stagnantwith respect to the entire refrigerant system, an actual flow amount ofthe refrigerant may be reduced if the liquid refrigerant is generated inthe high-pressure branch tube 45.

However, since the second electronic expansion valve 312 of thehigh-pressure valves 31 is in the opened state, the liquid refrigerantgenerated in the high-pressure branch tube 45 may pass through thesecond electronic expansion valve 312 and flow into the low-pressurebranch tube 46. Therefore, deterioration of the overall performance andefficiency of the refrigerant system due to the stagnant refrigerant inthe high-pressure branch tube 45 may be minimized. On the contrary, theperformance and efficiency may be rather improved when compared to thecase in which the high-pressure valves 31 are all closed during the fullcooling mode of the refrigerant system.

Moreover, according to the refrigerant system, the high-pressure valves31 that open and close the high-pressure branch tube 45 and thelow-pressure valves 32 that open and close the low-pressure branch tube46 may not only reduce the impact and noise caused by a pressuredifference between the refrigerants during the switching of theoperation mode of the indoor units 2, but also allow the liquidrefrigerant to flow from the high-pressure branch tube 45 to thelow-pressure branch tube 46.

As a consequence, the structure of the refrigerant system may be evensimplified when compared to the case in which a separate structure forreducing the impact and noise and a separate structure for introducingthe liquid refrigerant are further provided.

1. A refrigerant system comprising: an outdoor unit comprising: anoutdoor heat exchanger to heat-exchange a refrigerant and outdoor airwith each other; and a compressor to compress and to discharge therefrigerant; a plurality of indoor units, each comprising: an indoorheat exchanger to heat-exchange the refrigerant and indoor air with eachother, wherein at least one of the indoor heat exchangers evaporates therefrigerant; a high-pressure tube to guide the refrigerant dischargedfrom the compressor to the plurality of indoor heat exchangers; alow-pressure tube to guide the refrigerant evaporated in at least one ofthe indoor heat exchangers to the compressor; a high-pressure branchtube branched from the high-pressure tube to guide the refrigerant inthe high-pressure tube to at least one of the indoor heat exchangers; alow-pressure branch tube branched from the low-pressure tube to guidethe refrigerant in the at least one of the indoor heat exchangers to thelow-pressure tube; an indoor unit tube to connect the at least one ofthe indoor heat exchangers to both the high-pressure branch tube and thelow-pressure branch tube; and a high-pressure valve and a low-pressurevalve mounted on the high-pressure branch tube and the low-pressurebranch tube to selectively block the refrigerant flowing in thehigh-pressure branch tube and the low-pressure branch tube,respectively, wherein each of the high-pressure valve and thelow-pressure valve comprises an electronic expansion valve toelectronically control an opening degree thereof.
 2. The refrigerantsystem according to claim 1, wherein at least one of the high-pressurevalve and the low-pressure valve comprises two electronic expansionvalves, wherein the electronic expansion valves have differentcapacities.
 3. The refrigerant system according to claim 1, wherein thehigh-pressure valve comprises a first electronic expansion valve and asecond electronic expansion valve, wherein the second electronicexpansion valve has a smaller capacity than the first electronicexpansion valve, and the low-pressure valve comprises a third electronicexpansion valve and a fourth electronic expansion valve, wherein thefourth electronic expansion valve has a smaller capacity than the thirdelectronic expansion valve.
 4. The refrigerant system according to claim3, wherein the first electronic expansion valve is closed and therefrigerant in the high-pressure branch tube flows to one of theplurality of indoor heat exchangers through the second electronicexpansion valve when the indoor unit is switched to a heating mode. 5.The refrigerant system according to claim 3, wherein the thirdelectronic expansion valve is closed and the refrigerant in any one ofthe plurality of indoor heat exchangers flows into the low-pressurebranch tube through the fourth electronic expansion valve when theindoor unit is switched to a cooling mode.
 6. The refrigerant systemaccording to claim 1, wherein the high-pressure valve comprises a firstelectronic expansion valve and a second electronic expansion valve,wherein the first and second expansion valves are mounted in parallel onthe high-pressure branch tube, and the low-pressure valve comprises athird electronic expansion valve and a fourth electronic expansion,wherein the third and second expansion valves are mounted in parallel onthe low-pressure branch tube.
 7. The refrigerant system according toclaim 6, wherein the second electronic expansion valve and the fourthelectronic expansion valve have smaller capacities than the firstelectronic expansion valve and the third electronic expansion valve,respectively.
 8. The refrigerant system according to claim 7, whereinthe second electronic expansion valve is first opened, and then thefirst electronic expansion valve is opened when the indoor unit isswitched to a heating mode.
 9. The refrigerant system according to claim8, wherein the high-pressure valve and the low-pressure valve are closedbefore the second electronic expansion valve is opened when the indoorunit is switched to the heating mode.
 10. The refrigerant systemaccording to claim 7, wherein the fourth electronic expansion valve isfirst opened and then the third electronic expansion valve is opened,when the indoor unit is switched to a cooling mode.
 11. The refrigerantsystem according to claim 10, wherein the high-pressure valve and thelow-pressure valve are closed before the fourth electronic expansionvalve is opened, when the indoor unit is switched to the cooling mode.12. The refrigerant system according to claim 1, wherein thehigh-pressure valve is partially opened when all of the plurality ofindoor units operate in a cooling mode.
 13. The refrigerant systemaccording to claim 12, wherein the high-pressure valve comprises a firstelectronic expansion valve and a second electronic expansion valve,wherein the second electronic expansion valve has a smaller capacitythan the first electronic expansion valve, and the second electronicexpansion valve is partially opened when all of the plurality of indoorunits operate in the cooling mode.
 14. The refrigerant system accordingto claim 1, further comprising at least one distributor, wherein the atleast one distributor connects the outdoor unit to the plurality ofindoor units, wherein the high-pressure tube, the low-pressure tube, thehigh-pressure branch tube, and the low-pressure branch tube areconnected to the at least one distributor.
 15. The refrigerant systemaccording to claim 14, wherein the distributor comprises four pairs ofhigh-pressure tubes and low-pressure tubes to connect four indoor unitsto the distributor.